Ebola vaccine trials are underway in Guinea and Liberia, two of the three hardest-hit countries in the ongoing epidemic, and the CDC just announced a vaccine trial in Sierra Leone. Ebola has declined at different rates throughout Sierra Leone, which could impact the findings of a vaccine study. Their results show that the "stepped wedge" trial design originally planned would have been less likely to provide clear information than the phased-rollout randomized controlled trial that the CDC now plans to use.

By helping vaccine developers glean the information they need, the researchers are helping to put an end to future Ebola outbreaks.